Bottlehead Forum
Other Gear => Phono => Topic started by: Doc B. on April 16, 2013, 03:10:22 PM
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Anyone interested in our developing an AC motor controller kit for single and possibly three phase AC turntable motors?
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Yes! I have VPI...Thorens...Empire...need for all!
Cheers,
Geary
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Interesting..a tentative "yes" Vote
I don't know much about these, so forgive me...would it include some kind of platter speed measurement info fed back to the controller?And a basic display of this info?
Would/could it include an actual motor too?
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I could be depending on how flexible the design is. May motivate me to build up an Empire.
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Maybe, I have SOTA and VPI tables that may benefit but I really don't understand enough about it, time to do some homework :o
Robert Lees
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i am interested too. i do not understand enough of it myself but i have a rec-o-kut in the queue waiting to be reassembled. it has a synchronous motor that runs of the AC but i do not thinkthere is any kind of regulation....so yes definitely interested.
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Yes, Merrill mod AR XA here.
Suggestion to make it have adjustable so it may be used with tables with 115 line voltage motors and also low voltage AC motors.
There is a new 12V AC motor mod for my AR. A motor controller that could handle both the stock 115 volt motor and the new 12 volt motor would be kewl.
Some Pro-Ject/Music Hall tables have 16 volt AC motors too.
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Yes, interested also. Have a couple tables that could benefit.
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Another yes.
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I would be interested also.
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Hmmm, won't be of any use with my Clearaudio, but I do eventually plan to upgrade to either a refurbed Thorens TD-124 or a Kudzma Stabi-S / Stogi-S, and those would benefit.
-- Jim
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Ok, make that a definite... I bought the Kudzma table yesterday.
Anybody looking for a Clearaudio concept with soe extras, give me a shout.
-- Jim
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That Kuzma is a nice table!
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YES!!
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Where was this idea 2 years ago when I bought a P300?
Seriously now, I think it is a capital idea! If I didn't already have the P300 I would assuredly be in on it.
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Grainger,
I was just doing a bunch of research on power plants and conditioners andthe kind of control unit doc is talking about is far more accurate than the voltage regulation tolerances of even the best power plants.
Actually it's a different animal altogether as this kind of motor control regulates and allows for very fine adjustment of frequency whereas power plants are mostly designed for voltage stability -- and the PS Audio units seemed to have the largest voltage swing/lowest regulation tolerances -- 5% vs 3% for companies like PurePower.
I actually settled on a completely differentapproach -- an Equitech balanced power center -- no voltage regulation to speak of, but real, honest-to-goodness professional studio quality balanced power.
But if you are not jhaving any issues with speed control, the ps300 is probably good enough.
Another use for the kind of thing Doc is talking about is for 33 to 45, or maybe even 78 rpm switching without belt and pulley changes -- just turn up the frequency to get higher speeds. BPI used to make the PLC (which I used to own) which did sort of the same thing, and they also make the SDS -- synchronous Drive System, which is what it sounds like Doc is talking about here.
HTH,
Jim
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Jim,
You have a PM.
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I would be very interested in an AC motor controller kit!
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I use a variac before my Garrard 301 to adjust speed instead of using the garrard magnetic break. Would this control substitute the variac?
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Subscribed... ;)
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Giving this a bump to see if there is any decision or progress on this?
-- Jim
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No progress, we are still flogging the active step up idea, which is turning out to be quite a challenge.
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Doc, I have a VPI MK IV TT and have a real hard time justifying $1100 - $1300 for the VPI controller. So IMHO this is a GREAT idea. As long as it is reasonable in price sign me up.
Hopefully it is something that could be done soon.
Thanks,
Richard
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YES ;D
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I would like to echo that I have a VPI and I would love to be able to unplug it from my PS Audio power conditioner into a designated controller and be able to more accurately control the speed. It has to be tube rectified though ;) But also, as others have stated price concerns, if it is a $1,000 or more I probably won't buy it. For me, it needs to be in the $500 range and then I am very interested. I would wonder if it is even possible at that price point, but beyond that I would rather be honest and state upfront that I probably wouldn't spring for it. I would rather buy the Bee Pre!
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No progress, we are still flogging the active step up idea, which is turning out to be quite a challenge.
Just curious - is the motor controller topic dead?
Chris
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We are up to our necks in getting the DAC and a couple of other things out, which will keep us busy for the rest of this year. But I have already suggested that the motor controller should be put back on the table for consideration in 2015.
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I'm interested for sure. Forgive my ignorance, but could this design your considering be adaptable to rim drive? We have a pile of 3" thick 6061 Aluminum material at my shop, and I've been dreaming about a new DIY turntable with a 3" thick platter. I was considering trying to build a rim drive for the heck of it. Maybe a plywood prototype base, with the aluminum platter and a bearing (built in my shop). I figure if I'm building the platter and the drive pully, I can adjust the diameters to get the speed close, and dial it in from there. If it works good, then pull the platter and bearing ahead into a nice finished base. If the rim drive idea crashes and burns, it would be easy to use with a belt and pully. There's lot's of ground to cover here, and I'm at the dreaming stage. My current DIY table uses a Terres motor kit that measures a strobe disk on the bottom of the platter to maintain speed. It features a super simple homemade bearing, acrylic platter, and Rega RB250 with Incognito upgrades. I think it works and sounds pretty darn good, but i don't have much to compare it too.
Pfenning
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I helped a friend set up something to drive a rim-drive table, really made much more difference than I expected. I don't mind making some electronic designs, but the big question is, what are the requirements - voltage and current? Sine-wave distortion? What tables might need the most power?
Pretty much anything will drive an old AR, but how about a Rek-O-Kut? I can easily see a low-power source that overloads on startup but eventually gets the platter going, and then keeps it going well.
Probably we should build something and try it out ...
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Something like this maybe: ;)
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The mechanical aspect seems pretty easy to me. I can figure out how to build the drive wheel, bearing, and platter, but I'm lost when it comes to electrical design, and motor specifications.
Pfenning
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I have had a bookmark to Pabst Synchronous motor. I'll find it and get back to you.
I'm assuming you can make the idler wheel and calculate the circumference versus motor RPM. Right now I couldn't.
I'm smoking a turkey today and am on and off line.
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It is hard typing now, I was scalded moving the turkey on the fire.
Here is a link to a motor manufacturer you can buy synchronous turntable motors from.
http://www.hurst-motors.com/papbdirectdrive.html
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Thanks for the link Grainger. I hope your ok from the scalding, I know how easy accidents can happen when working around the grill. On the motor, how do I regulate the speed to dial it in? I can calculate the idler diameter, and build it (i think) to a high precision diameter, but how do I make slight adjustments in the speed to get it exact? How close will the motor run to the specified rpm? There has to be some tolerance on that, but how much? I hope your feeling better today.
Pfenning
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snip...On the motor, how do I regulate the speed to dial it in? I can calculate the idler diameter, and build it (i think) to a high precision diameter, but how do I make slight adjustments in the speed to get it exact? How close will the motor run to the specified rpm? There has to be some tolerance on that, but how much?
Pfenning
The speed of an AC asynchronous motor is driven by the line frequency. In an ideal situation, you get 60Hz at the outlet and the motor runs at the specified RPM. It is up to you to determine the motor pulley/ platter diameter ratio to generate the desired speed. In reality there are slight frequency deviations at the outlet and motors don't always run quite to spec. Additionally, bearing friction, wear , ambient temperature and lubrication will impact the delivered speed.
A good TT AC motor controller will synthesize a "perfect" 60Hz sine waveform. You can adjust the frequency of the regenerated sine wave to speed or slow the motor allowing for fine adjustment to the platter speed. Simple to describe, much harder to design, manufacture and keep costs reasonable.
It is also beneficial to reduce the voltage once the initial torque to bring the platter to speed is achieved. This will reduce vibration in the motor for quieter operation.
Cheers,
Geary
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Exactly, what Geary said. All AC tables made today that do not include a speed controller rely on the power department to keep the frequency stable. I don't think it stays off frequency for long but has periodic wavering.
The benefits I see from a dedicated speed controller are as Geary says. First, you get a stable 60 Hertz with no wandering or wavering. Second you get the voltage drop after startup. The motor torque that brings the platter to speed in a revolution or two causes hunting, dither, once the platter is at speed. Dropping the voltage drops the current and the current causes the torque. So once at speed less torque gives a steadier speed.
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Ok, so I understand the motor speed is set based off the 60 hertz. How do I build a speed controller like you and Geary mention? I follow you on the torque reduction idea. Can I rob the design from an existing TT (TD124 or ???)? I'm confident in my ability to build the mechanical items, but I'm pretty lost on the motor controller stuff. I need a pretty clear path to follow.
Pfenning
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I think that Dan and the Bottlehead crew is going to come up with a kit. I hope so.
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Ok, so I understand the motor speed is set based off the 60 hertz. How do I build a speed controller like you and Geary mention? I follow you on the torque reduction idea. Can I rob the design from an existing TT (TD124 or ???)? I'm confident in my ability to build the mechanical items, but I'm pretty lost on the motor controller stuff. I need a pretty clear path to follow.
Pfenning
I would not considering designing and building your own controller. It is a sophisticated device that requires considerable electronics and microprocessor expertise. There was a DIY design, short lived, Mark Kelly Synchrotron AC-1 Drive Controller. Mark sold a basic board. It worked well, but, IIRC, was difficult to build and maintain. They occasionally pop up used, but I would be wary as to why!
Until BH does a controller kit, I would focus on building the TT, (no small task!), with plans to pair it with a commercially available AC controller. A used VPI PLC can be had for about $300, the much more sophisticated SDS , used for $800-900. You can source a new unit for about $380 from Phoenix Engineering , the Falcon PSU Turntable Speed Controller. There are probably a few others of which I am not aware.
I think Doc realizes that there is a DIY market for the controller, but it may well morph into the same manufacturing issues that the DAC faced. Not a small undertaking!
Cheers,
Geary
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The TD-124 uses a shaded pole motor. It's speed control involves moving the idler on a stepped pulley that is connected by a belt to the motor. Fine speed control is done by putting drag on the pulley with a magnet with a moving shield to control the magnet's field. The motor speed is, so far as I can tell, immune to fluctuations in frequency, but sensitive to changes in voltage. DIYing this design, would be an incredible pain (and cost way more than buying a 124)
There are a lot of pages about DIYing tables. This looks pretty comprehensive:
http://www.altmann.haan.de/turntable/
Reading pages by people who have actually built these things is probably more useful than forum postings by a bunch of people who switch up cheap beer and motors. Also, I'd focus more energy on the bearing than the motor. The motor will be swappable and tuneable if you're unhappy with the results. A lousy bearing will create all kinds of problems, and be way harder to change.
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...snip
Reading pages by people who have actually built these things is probably more useful than forum postings by a bunch of people who switch up cheap beer and motors.
This comment bothers me. I realize that it is hard to judge intent on the web, so hopefully this was meant to be funny? Pabst is a well known German motor manufacturer. About ten years after Thorens discontinued the TD124, they chose Pabst to provide replacement motors. So I don't think Grainger is switching up "cheap beer and motors".
Pfenning was quite clear that he is reasonably confident in his mechanical abilities regarding the build. Perhaps more so than the author of the DIY turntable site referenced. Pfenning was specifically asking for input on the electronics and motor. That was the focus of the responses.
Cheers,
Geary
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There was never a _Pabst_ motor for the TD-124...
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There was never a _Pabst_ motor for the TD-124...
I consider the Analogue Department one of the authoritative sites regarding Thorens. Perhaps you'll take a look.
http://www.theanalogdept.com/papst_aussenlaufer.htm (http://www.theanalogdept.com/papst_aussenlaufer.htm)
"
back to the TD124 dept.
A Papst in a Thorens?
The story goes something like this:
In 1977, ten years after the TD124 had been discontinued, Thorens management worried that it could no longer supply new replacement motors for their once top-of-the-line player. The solution turned out to be the subject of this article. Thorens contracted with Papst to adapt one of their "Aussenlaufer" motors to function in the TD124.
Above photo: A 60 hz version of the Papst Aussenlaufer motor designated by Thorens for use in the TD124. It stands on chassis sn # 13943, which has been chemically stripped of its paint in preparation for a complete restoration.
About the Papst:
Thorens Service Bulletin Nr. 22, October 1977
In German
Service 22_pge 1a.jpg (311073 bytes)pge 1
Service 22_pge 2a.jpg (401314 bytes)pge 2
(roughly)Translated into English:
THORENS -- Service Information Nr. 22 Oct. 1977
Replacement Motor for Thorens TD 124
The continuing popularity of Thorens turntable TD 124 has led us to search out a solution for the replacement motor. We are therefore very pleased to finally introduce adequate replacement in the form of a motor manufactured by Papst.
Unfortunately, due to the completely different type of construction, and an alternative electrical suppressor circuit, the motor can only be operated with one voltage option.
To order, it is important to specify which kit:
3805-200 Kit for 200-240 V at 50 hz (with C = .47 uF) or
3806-110 Kit for 100-125 V at 60 hz (with C = 1.4 uF)"
Cheers,
Geary
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Yes. Steve Clarke knows his shit. He knows what a Papst motor is.
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I do think Josh is getting a little revved up here, but c'mon Grainger, Pabst is beer. The company that makes the motors is Papst. Finding a link for a mispelled search word on Google doesn't automatically make it the American spelling - yet.
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I do think Josh is getting a little revved up here
The real question here is whether he's sticking up for PBR (he does drink the stuff) or his turntable...
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Wow, I commented on a post concerning Josh, who drinks PBR, not you. Josh also has a turntable with a Papst motor in it, while you have a VPI?
Frankly, Grainger, you are on the border of flaming here. I'm locking this post for now.
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Where I stand is with Peebs. This thread is, unfortunately, locked.
My suggestion is for everyone here -
Remember this is a hobby, not Congress. If someone rubs you the wrong way just ignore him.